In the last few years, astronomers have seen a couple of gigantic and nearly perfectly circular radio objects out in the remote universe. Though no one has an explanation for all these mysterious things yet, a group has recently added another person to their catalog, potentially moving them closer to solving this head-scratcher.
The enigma started shortly after the Australian Square Kilometre Array Pathﬁnder (ASKAP), a bank of 36 colossal dishes in Western Australia that scans the skies in the radio part of the electromagnetic spectrum, began creating maps of the whole night sky in 2019.
ASKAP scientists were mostly searching for smart resources that could indicate the presence of black holes or huge galaxies glowing in waves. But some from the group are always on the hunt”for whatever is weird, whatever is new, and whatever resembles nothing else,” Bärbel Koribalski, a galactic astronomer in Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Western Sydney University in Australia, advised Live Science.
In the data, group member Anna D. Kapińska of the National Radio Astronomy Observatory in Socorro, New Mexico, spotted four glowing radio circles, Koribalski recalled, though originally the remainder of the researchers dismissed them as a familiar phenomenon.
But when telescopes tried to examine the items in different wavelengths, such as the optical light our eyes use to view, they turned up empty, leading the group to dub them odd radio circles (ORCs).
Even stranger, every one of the ORCs needed a galaxy perched nearly exactly in its center, like a bullseye. The astronomers could determine the entities were every several billion light-years away and potentially as big as a couple of million light-years in diameter.
Nobody had seen anything like these before, and in a paper published this past year, the team offered 11 possible explanations about what they could be, such as imaging glitches, warps in space-time called Einstein rings, or even a new sort of remnant out of a supernova explosion.
The researchers have since scanned the heavens with ASKAP and discovered one more ORC to add to their own collection, a thing about 1 million light-years across situated approximately 3 billion light-years away. They published their findings on April 27 to the preprint database arXiv, and they’ve been approved for publication in the Monthly Notices of the Royal Astronomical Society.
The group has narrowed their ideas down to three potential explanations, Koribalski said. The first is that perhaps additional galaxies are forming a bunch close to the item and bending bright material to a ring-like construction. These may just be too feeble to be picked up by current telescopes.
Still another possibility is that the central supermassive black hole of these galaxies is swallowing gas and dust, producing humongous, cone-shaped jets of particles and energy. Astronomers have often seen such happenings in the universe, though normally the jets align in this way with Earth which observatories view them as moving out of the surfaces of the galaxy.
Maybe in the event of these ORCs, the jets are simply pointing directly towards our planet, Koribalski indicated, so that we’re in nature looking down the barrel of a long tube, creating a circular, two-dimensional image around a central galaxy.
“The other explanation is exciting,” she said. “This could be something entirely new.”
Some unknown but highly energetic events likely took place in the center of these galaxies, creating a burst wave that traveled out as a world and caused a ring structure. Kowalski isn’t yet sure what sort of event could leave such a signature, though perhaps it is a formerly unknown product of crashing black holes such as the type seen in atmospheric waves at the Large Interferometer Gravitational-Wave Observatory (LIGO) in America.
However, Harish Vedantham, an astronomer at the Netherlands Institute for Radio Astronomy that wasn’t associated with the job, favors the easier idea — which the ORCs are a reflection of a well-known phenomenon, and so are bright jets shooting from a galaxy at a seldom seen angle.
Vedantham is advised in this by the principle of Occam’s razor, which prefers ordinary explanations over odd, brand new ones. “You can construct an exotic scenario,” he advised Live Science. “However, the easiest answer is almost always correct.”
In a similar vein, the chance that an ORC is an invisible galactic cluster isn’t appealing to him because “it’s kind of hard to hide a bunch,” he said. The objects are far away, but they are not that much, so at least a couple additional galaxies ought to be noticeable, he added.
Two Vedantham and Koribalski concur that more telescope observations in different wavelengths should help scientists have a better idea about what is happening. New data will be coming in another six months or so, ideally adding added ORCs for their catalog, Koribalski explained.
Meanwhile, she’s somewhat enjoying the puzzle. “You become a detective. You look at all the clues and weigh them up against each other,” she said.